\begin{tikzpicture}
    \tkzDefPoints{0/0/O}
    \tkzDefPoint(60:1.5){A}
    \tkzDefPoint(205:1.5){B}
    \tkzDefPoint(335:1.5){C}

    \tkzDrawPolygon(A,B,C)
    \tkzDrawCircle[thick](O,A)
    \tkzDrawPoint(O)
    \tkzLabelPoints[above](A)
    \tkzLabelPoints[left](B)
    \tkzLabelPoints[right](C,O)
\end{tikzpicture}

